Micrometer



J. J. DAVIS. MICROMETER.

APPLICATION FILED SEPT. 23. 1919.

Patented May 25, 1920'.

Inventor:

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UNITED fiTAES @FFMIE...

JOHN JONES DAVIS, OF YOUNGSTOWN, OHIO.

Y J IVIICROMETER.

Application filed September 23, 1919.

To all whom it may concern:

Be it known that 1, JOHN J. DAVIS, a citizen of the United States, and resident of Youngstown, Ohio, have invented certain new and useful Improvements in Micrometers, of which the following is a specification.

My present invention relates to improvements in micrometers designed more especially for determining the thickness of sheet metal sheets.

The invention aims to provide a device of extreme simplicity and durability and one by which the gage of each sheet measured will be indicated in thousandths of an inch and also what are known as U. S. standard gage and Birmingham wire gage readings.

The invention also aims to provide a construction which may be easily manipulated to gage the thickness of the sheet at a considerable distance from the edge thereof.

With these and other objects in view the invention includes the novel features of construction and arrangement and combination of parts hereinafter described and particularly pointed out in the appended claims.

an embodiment of my invention is illustrated in the accompanying drawings, in which:

Figure 1 is a plan view of the micrometer.

Fig. 2 is a side elevation.

Fig. 3 is a detail view of the upper arm.

Fig. 4 is a detail View of the lower arm.

Fig. 5 is a detail view of the spring.

Fig. 6 is a sectional view showing the ratchet and spring and the sleeve inclosing the spring.

Fig. 7 is a view of the bushing.

Referring by reference characters to this drawing the numeral 1 designates the body or frame of the micrometer which is of substantially fork shape having two parallel arms 1 and 1 the former of which is of considerably greater length than the latter.

The opposite end is provided with a suitable handle 2 which is preferably arranged lengthwise of the frame.

The lower arm 1 is split as indicated at Z) and is provided with a threaded opening to receive the threaded contact point or member which, by means of the kerf 3 may be adjusted in or out, and clamped in any desired position by the clamping screw 4 threaded througha transverse opening in the split extremity of the arm 1".

Specification of Letters Patent.

Patented May 25, 1920.

Serial No. 325,704.

The upper arm 1 is provided with a cylindrical opening a in which is seated a cylindrical bushing 5 having an internal screw thread to receive the upper contact screw 6 and this bushing is clamped firmly in position by the transverse clamping screw 7, the portion of the arm l beyond the cylindrical opening being split as indicated at a. The bushing is preferably provided with an upper marginal flange.

The dial plate is of circular disk shape as indicated at A and is provided around its periphery with suitable graduations and indicating numerals so that measurements may be read in thousandths of an inch and in U. S. standard and Birmingham wire ga readings. The said plate has a central open ing through which the bushing 5 passes, and it is secured to the upper face of the frame by screws 7 tapped into the frame. A pointer arm 8 has an opening at one end through which the bushing passes, being held in position on the bushing by the overlying flange 5. The pointer carries an upright post or projection 8 which engages an opening in the end of the pointer guide or operating arm 9 which latter has an opening through its opposite end to permit the arm to be seated on the stem of the screw 6 to which it is fixed to turn with the screw as one body. Above this arm there is a sleeve or bushing 10 which encircles the stem 6 of the screw 6. Within this sleeve there is a spring 13 which is fixed at its lower end to the arm 9 and at its upper end it is provided with a bent portion 3 to provide a pawl like member to engage the ratchet teeth 11 on the under side of a milled disk or thumb wheel 11. This wheel is held by a screw 12 seated in a tapped opening in the end of the stem 6 of the screw 6, the said wheel being turnable about the screw. The sleeve 10 serves to inclose the spring.

In the operation of the gage the pointer is turned around the dial by the operator grasping the thumb wheel and turning the screw 6. The impelling arm 9 moves with the screw 6 and thus impels the pointer by means of the post 8 until the lower end of the screw 6 seats itself on the sheet being gaged and presses it lightly between itself and the lower gage point, i. 6., the upper end of the screw 3. When gaging contact has taken place further turning force applied to the thumb wheel will be ineffective in setting the gage screw 6 harder upon the an I sheet owing to the fact that the ratchet teeth will then slip over the inclined pawl end 13 of the spring 13 and thus danger of an inaccurate reading, due to further turning force applied to the thumb wheel will be avoided. It, therefore, will be observed that the turning direction of the thumb wheel in advancing the screw 6 toward the other point or screw 8 will be in the direction of the arrow and consequently the ratchet teeth can slip over the pawl-like end of the spring when resistance to the springs bodily turning is created by the gage point properly contacting the sheet.

Having thus described my invention what I claim is 1. In a micrometer a forked member having a deep bifurcation at one end and a handle projecting from the other end in substantial alinement with said bifurcation, a rigid contact member carried by one arm, an opposed contact screw threaded through the opposite arm, a dial plate secured to said arm, a pointer arranged to swing about the axis of the opposed screw, means for rotating said opposed screw, and means for causing said pointer to be moved in unison with said opposed screw.

2. In a micrometer a forked member or frame, a rigid contact member carried by one arm thereof, a bushing carried by the other arm, a dial plate carried by said other arm, a pointer rotatable about said bushin an opposed contact screw threaded through said bushing, a member for rotating said opposed screw, and an arm connected with said screw and having a vertical slip joint connection with the pointer.

3. In a micrometer a forked member or frame, a rigid contact member carried by one arm thereof, a bushing carried by and fixed to the other arm, a dial plate carried by said other arm, a pointer rotatable about said bushing, an opposed contact screw threaded through said bushing, a member for rotating said opposed screw, a guide arm connected with said screw, and having a recessed outer end, and a post carried by the pointer and slidably engaging said recessed end.

4. In combination, a dial, an arm carrying the same, a screw threaded gaging member passing through the center of the dial, and through the arm, a fixed gaging point, a pointer, a thumb wheel and a pawl and ratchet connection between the screw and the thumb wheel, substantially as described.

5. In combination, a dial, an arm carrying the same, a screw threaded gaging member passing through the center of the dial and through the arm, a fixed gaging point, a pointer, a thumb wheel and a pawl and ratchet connection between the screw and the thumb wheel, said pawl and ratchet comprising a spring member and ratchet teeth, substantially as described.

6. In combination, a dial, an arm carrying the same, a screw threaded gaging member passing through the center of the dial and through the arm, a fixed gaging point, a

pointer, a thumb wheel and a pawl and ratchet connection between the screw and the thumb wheel, said pawl and ratchet comprising a spiral spring surrounding the stem of the screw, attached at its lower end to said screw and ratchet teeth on the thumb wheel engaging the end of the spring, substantially as described. 7

7. In combination, an arm having a fixed gage point, a second arm spaced apart therefrom, a bushing fixed in said second arm, screw threaded internally, and having a flange, a dial, a pointer turnable about the bushing under the flange, a screw threaded gage member passing through the bushing, a slip joint connection between the screw and the pointer, a thumb wheel and a pawl and ratchet connection between the thumb wheel and the screw, substantially as de scribed.

In testimony whereof li aflix my signature.

JOHN JONES DAVIS. 

